Conventional refrigeration systems, such as found in automotive air conditioning applications, include a compressor, a condenser, an expansion device, and an evaporator. Refrigerant is circulated through the system to produce cooling. Energy is provided to the system by the compressor which serves to create a source of high pressure gas (or vapor) refrigerant which is allowed to pass through the condenser. The refrigerant dissipates heat in the condenser and changes state to a high pressure liquid. The refrigerant then passes through the expansion device and into the evaporator where the refrigerant changes from a high pressure liquid to a low pressure liquid, and subsequently to a low pressure gas. The change of state removes heat from the area surrounding the evaporator. The refrigerant is then drawn from the evaporator back to the compressor in a low pressure gas form, where it is again compressed into high pressure gas for repetition of the cycle.
An accumulator is normally located between the evaporator and the compressor. The accumulator ensures that only refrigerant in a gas stage passes into the compressor, as refrigerant from the outlet of the evaporator often includes both a liquid component and a gas component.
A heat pump system is similar to a refrigeration system, but operates in reverse to produce heating, rather than cooling. A reversing valve downstream of the compressor can be used when the system is intended to operate in both a heating and cooling mode.
In both a refrigeration and heat pump system, the compressor normally introduces oil into the gas stream exiting the compressor. In a refrigeration system, the oil can coat the interior walls of the downstream condenser and reduce the efficiency and heat transfer of the condenser, and generally serves no purpose downstream of the compressor. For maximum efficiency, the oil may be removed from the gas stream exiting the compressor and returned to the suction line of the compressor. In a heat pump system, the oil can be returned to the compressor, or can be directed downstream to lubricate downstream components.
An oil separator is normally located in the discharge line of the compressor in both a refrigeration and heat pump system to separate the oil from the gas and direct the oil-free gas downstream of the compressor. The separator may also be equipped to filter the oil to remove harmful particulates in the oil. The oil can then be returned to the system, such as to the suction line of the compressor, introduced back into the gas stream, or directed to other appropriate components in the systems such as sumps, accumulators, pumps, oil float controls and valves, etc. In a refrigeration system, the oil separator ensures that only oil-free gas passes from the compressor to the condenser to maintain the condenser at maximum efficiency; while in a heat pump system, the separator filters the oil to prevent damage to downstream components.
In order to remove the oil from the gas stream, some oil separators impart a tangential flow pattern to the oil/gas mixture entering the housing, such that centrifugal forces will cause the oil droplets to be directed outwardly against the inside walls of the housing. The oil droplets will then coalesce and drip downwardly under gravity into a collection area, where the oil can then be removed.
One such oil separator is shown in U.S. Pat. No. 5,551,253. This separator includes a housing enclosing an upper perforated baffle plate, a lower perforated baffle plate and a filter disposed between the baffle plates. Oil and gas passing through the baffle plates and filter exits the lower baffle plate through guiding holes which impart a swirling component to the mixture. The oil in the mixture is displaced outwardly by centrifugal forces against the interior walls of the housing beneath the baffle plate and filter assembly, and then gravitates downwardly for collection at the bottom of the chamber. The oil-free gas is discharged through an outlet pipe positioned centrally within the chamber. An apertured separating plate is situated between the lower buffer plate and the collected oil to isolate the collected oil from the swirling gas.
Other oil separators have an inlet conduit which introduces the oil/gas mixture tangentially into the housing to achieve the same results. These separators are shown for example in U.S. Pat. Nos. 2,511,967, 4,690,759, 3,778,984 and 4,263,029. Another oil separator is shown in U.S. Pat. No. 4,478,050, where a series of deflector tabs are provided along the walls of the housing to assist the tangential flow of the mixture.
Still another oil separator is shown in U.S. Pat. No. 5,113,671. In this patent a helical wall or auger is provided between the gas outlet conduit and the peripheral wall of the housing to cause the oil/gas mixture to flow in a largely circumferential path along the peripheral wall. The flights of the helix extend substantially radially outward from the central axis (surrounding the outlet conduit) to the peripheral wall of the housing. The oil droplets in the gas collect on a screen around the inside surface of the wall and drip downwardly. An inverted funnel/baffle at the lower end of the housing includes apertures which drain the oil into a lower collection area for removal. U.S. Pat. Nos. 5,271,215, 5,404,730, 5,553,460 and 4,263,029 show similar helical walls or augers operable to separate the oil from the incoming oil/gas mixture.
While the above oil separators appear to have enjoyed some acceptance in the market place, they require a considerable length to effectively remove oil from the gas stream with a tangential flow path. This requires the housing to be relatively long, which increases the material costs, as well as requires additional space in the refrigeration system. It is therefore believed desirable to reduce the size of the separator, while still maintaining effective separation of oil from the oil/gas mixture, and filtering of the oil.
Compressor-induced gas pulsations may transmit objectionable noise to downstream components. Many systems require a muffler to reduce this noise. It is therefore believed also desirable to reduce the noise levels in the oil separator.
Still other oil separators can be overwhelmed during start-up of the system where a slug of liquid refrigerant and entrained oil from the compressor can pass to the separator. The refrigerant and oil can clog the filter media when the media is disposed between the inlet and outlet (such as shown in U.S. Pat. No. 5,551,253), and cause an undesirable pressure drop across the separator while the oil and refrigerant drain through the media. It is therefore believed that there is a demand for an oil separator which prevents pressure drops across the separator-even during difficult conditions such as at start-up of the system.
It is further believed that there is a continual demand in the industry for an oil separator which effectively and efficiently separates oil from the gas stream, directs the oil-free gas to the downstream components, and filters the oil, and then directs or returns the filtered oil to the appropriate components in the system.